Endosseous, i.e., intra boney, implants are commonly used to support fixed or removable prostheses where a patient's natural roots have been lost, and as a consequence, support is lacking to provide an adequate foundation onto which the dentist can rebuild a dentition. As the aging population retains more of their natural teeth, and as the younger generations want to take advantage of more conservative approaches offered by implant dentistry, e.g., using a single implant rather than cutting down adjacent teeth to support a short span bridge to replace a missing tooth, implant dentistry has gained more and more popularity and has moved into the mainstream of dentists worldwide.
The current implant design is based on an endosseous fixture, a titanium screw that acts as an artificial root. Branemark, Tissue-Integrated Prostheses (1985). Modifications made to the endosseous fixture have centered on the macro structure of the implant (e.g., by exchanging the screw with a press-fit/cylindrical implant, a stepped screw or cylinder, or a tapered screw or cylinder), (Brunski J. B., Biomechanics Of Oral Implant,. Future Research Directions NIH Consensus Development Conference on Dental Implants, 1988; Kirsch A. et al., The IMZ Osseointegrated Implant System, Dent. Clin. North Am. 1989 (4), 33:733-791; Niznick G. A., A Multimodal Approach To Implant Prosthodontics, Dent. Clin. North Am. 1989 (4), 33:869-878; Wennerberg A. et al., Design And Surface Characteristics Of 13 Commercially Available Oral Implant Systems, Id. 1993:8:622-633; Siegele D. et al., Numerical Investigations Of The Influence Of Implant Shape On Stress Distribution In The Jaw Bone, Id., 1989:4:333-340; Olsson M. et al., MkII-a Modified Self-Tapping Branemark Implant: 3-Year Results, Id. at 1995:10:15-21; Langer B. et al., The Wide Fixture: A Solution For Special Bone Situations And A Rescue For The Compromised Implant, Part 1, Id., 1993:8:400-408; Schnitman P. A. et al., Implants For Partial Edentulism, NIH Consensus Development Conference On Dental Implants, 1988), on the micro structure (e.g., surface modifications such as use of machined titanium, blasted titanium, titanium alloy, acid-etched titanium, plasma-sprayed titanium and hydroxyappatite coating, growth factors, and proteins), (Baier R. E. et al., Future Directions In Surface Preparation Of Dental Implants, NIH Consensus Development Conference On Dental Implants, 1988; Young F. A., Future Directions In Dental Implant Materials Research, Id.; Krauser J., Hydroxylappatite-Coated Dental Implants, Dent. Clin. North Am. 1989, 33:4:879-903; Buser D. et al., Tissue Integration Of One-Stage ITI Implants: 3-Year Results Of A Longitudinal Study With Hollow-Cylinder And Hollow-Screw Implants, Int. J. Oral Maxillofac. Implants, 1991:6:405-412), on one-vs-two-stage designs, (Weber H. P. et al., Comparison Of Healed Tissues Adjacent To Submerged And Non-Submerged Unloaded Titanium Dental Implants, Clin. Oral Impl. Res. 1996:7:11-19; Busser D. et al., Tissue Integration Of One-Stage ITI Implants: 3-Year Results Of A Longitudinal Study With Hollow-Cylinder and Hollow-Screw Implants, Int. J. Oral Maxillofac Implants 1991:6:405-412), and on modifying the connection between the implant and its abutment (e.g, either internal hex, external hex, standard hex, tall hex, wide hex, etc.), (U.S. Pat. No. 4,960,381; U.S. Pat. No. 5,407,359; U.S. Pat. No. 5,209,666; U.S. Pat. No. 5,110,292).
Irrespective of the design variables discussed above, current systems have two general characteristics in common: First, the abutment-implant interface is planar; and second, the area intended for bone apposition, i.e., osseointegration, terminates parallel to the abutment-implant interface, 360 degrees around the implant.
Traditionally, endosseous implants were designed for treatment of the fully edentulous patient. In general, this particular patient population exhibits reduced bone-tissue volume, both in height and width when compared to the partially edentulous patient with recent or impending tooth loss. However, the bone-tissue morphology of partially edentulous patients significantly differs from that of fully edentulous patients, in that the naturally occurring supporting bone structures reveal a scalloped architecture around the tooth.
Currently available implant technology does not take the different bone-tissue morphologies into consideration. Heretofore use of an implant with an intended bone-tissue apposition surface parallel to a flat abutment-implant interface has led to either (1) placement of soft-tissue intended parts of the implant within bone-tissue, leading to bone-tissue resorption in these areas, and/or (2) exposure of hard-tissue intended surfaces to the soft tissue, resulting in possible peri-implant infections due to bacterial colonization around the rough surface and potential loss of the implant.